Thank you very much for this reference, Dag
"Dag Stenberg" <dag.stenberg at nospam.helsinki.fi.invalid> wrote in message
news:bacile$5vs$1 at oravannahka.helsinki.fi...
> Shu Y, Hasenstaub A, McCormick DA
> Turning on and off recurrent balanced cortical activity
> Nature 423(6937) : 288-93 (2003)
>> The vast majority of synaptic connections onto neurons in the cerebral
> cortex arise from other cortical neurons, both excitatory and
> inhibitory, forming local and distant 'recurrent' networks. Although
> this is a basic theme of cortical organization, its study has been
> limited largely to theoretical investigations, which predict that local
> recurrent networks show a proportionality or balance between recurrent
> excitation and inhibition, allowing the generation of stable periods of
> activity. This recurrent activity might underlie such diverse operations
> as short-term memory, the modulation of neuronal excitability with
> attention, and the generation of spontaneous activity during sleep. Here
> we show that local cortical circuits do indeed operate through a
> proportional balance of excitation and inhibition generated through
> local recurrent connections, and that the operation of such circuits can
> generate self-sustaining activity that can be turned on and off by
> synaptic inputs. These results confirm the long-hypothesized role of
> recurrent activity as a basic operation of the cerebral cortex.